Method of making three-phase cores for transformers



G. A. SMITH 2,964,836 METHOD OF MAKING THREE-PHASE CORES FOR TRANSFORMERS Dec. 20, 1960 2 Sheets-Sheet 1 Original Filed Dec. 13, 1954 INVENTOR GEORGE A SM TH T1 :15. MY :W

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Dec- 1 G. A. SMITH 2,964,836

METHOD OF MAKING THREIEPHASE CORES FOR TRANSFORMERS Original Filed D60. 13, 1954 2 Sheets-Sheet 2 INVENTOR GEORGE A. SMITH United States Patent Ofilice 2,964,836 Patented Dec. 20, 1960 METHOD OF MAKING THREE-PHASE CORES FOR TRANSFORMERS George A. Smith, Pine Bluff, Ark., assignor to Central Transformer Corporation, Pine Bluff, Ark., a corporation of Arkansas Original application Dec. 13, 1954, Ser. No. 474,813,

now Patent No. 2,889,525, dated June 2, 1959. Divided and this application Oct. 20, 1955, Ser. No. 541,585

4 Claims. ('Cl. 29-15557) This invention relates to magnetic cores, and particularly to three-phase magnetic cores, adapted for use in induction apparatus such as transformers, and to the method of making same.

This application is a division of my copending application Serial No. 474,813, filed December 13, 1954, now Patent No. 2,889,525.

The invention particularly relates to the formation of three-phase core structures from strip-like magnetic metallic ribbon, preferably of the type in which the grain of the metal is oriented in the direction of magnetic flux, and provides new and novel improvements in three phase transformer cores.

There have been numerous attempts to employ magnetic strip material in the formation of three-phase magnetic cores. and various forms and shapes of connecting yoke portions have been employed for interconnecting the winding leg portions of such cores. This invention is particularly directed to such transformer cores which include substantially T-shaped yoke portions. In previously proposed construction difficulties of assembly particularly in the associating of the phase windings with the respective winding legs have been encountered, and, although attempts have been made to overcome these diificulties of assembly, such attempts have re sulted in impairing the efficiency and desirability of operation of the core structure.

Thus it has heretofore been contemplated that a continuous coil of strip material might be employed to provide two of the winding legs with a laminated third leg associated therewith. The employment of such a continuous wound coil has presented the difiiculty of requiring the unwinding of the coil and the insertion of the free end thereof successively through the windows of the phase windings, continuing the rewinding until the previously wound coil has been completely inserted into the phase windings. To obviate the difiiculty of this type of situation it has been proposed in some instances to sever the respective winding legs in order to pro.- vide for the removal of a yoke portion, permitting the simple mounting of the phase windings upon the winding legs, followed by the replacement of the severed yoke portions. This procedure has resulted in unsatisfactory performance because of the multiplicity of butt joints employed in reassociating the severed yoke portion with the winding leg portions.

Other types of solutions of this problem have been suggested, as for example a multiplicity of individual bundles of laminations have been associated together. The resultant structure has been faced with operational difliculties similar to those encountered in the severedleg type of construction mentioned above, necessitating an excessive plurality of joints between the associated parts. Such excess of jointing is primarily inefficient in producing undesirable sound level characteristics, and by unsatisfactorily increasing magnetic losses, a condition inherent in jointing magnetic material.

The present invention is primarily directed to a threephase core for transformers formed of a multiplicity of lamination layers of magnetic strip material which provides a maximum facility of associating phase windings with the winding legs of the core while reducing to a minimum the hitherto unsatisfactory plurality of joints among the respective lamination layers. 7

In particular this invention contemplates the production of a three-phase transformer core in which a series of substantially rectangular or quadrilateral lamination layers are nested together to provide a substantially rectangular stack including two winding legs and connecting yoke portions, and a third leg is provided by associating a substantially U-shaped bundle of nested lamination layers including a winding leg portion and upper and lower yoke portions with the substantially rectangular stack. In further particular the respective substantially rectangular lamination layers are independent each of the other and are substantially continuous, being interrupted along one of the connecting yoke portions to provide for access of phase windings to the winding leg portions, and in the preferred embodiment the interrupted yoke portions are alternately disposed at opposite ends of the nested stack ultimately formed in the fabrication of the core. 7

The principal object of the present invention is to provide a new and novel method of producing threephase core transformers.

A further object of the invention is to provide such a method of producing a three-phase core which includes forming a substantially rectangular stack of independent quadrilateral lamination layers, one of the sides of each of the layers being interrupted for access, and the re mainder of each of the layers being continuous and uninterrupted.

A further object of the invention is to provide such a transfromer core producing method in which the respective interrupted sides of successive said quadrilateral lamination layers are alternately disposed at opposite ends of the substantially rectangular stack.

A further object of the invention is to provide a method of fabricating a three=phase core for transformers which includes the steps of nesting a series of quadrilateral lamination layers to form a substantially rectangular stack, and associating a U.-shaped bundle of lamination layers therewith to provide three substantially parallel winding legs for receiving phase windings of transformers.

A further object of the invention is to provide such a transformer core producing method including forming a rectangular stack of quadrilateral lamination layers and providing a third winding leg by associating a U-shaped bundle of lamination layers with the stack, at least part of the lamination layers of the U-shaped bundle being interleaved between adjacent quadrilateral lamination layers.

A further object of the invention is to generally improve the efficiency' and facility in methods of making three-phase transformer and the cores for same.

The means by which the foregoing and other objects of the present invention are accomplished and the manner of their accomplishment will be readily understood from the following specification upon reference to the accompanying drawings, in which:

Fig. 1 is a face view of a susbtantially rectangular coil of magnetic strip material; r

Fig. 2 is a face view of a coil like the coil of Fig. 1, with one of the short sides divided as by cutting to provide a nest of susbtantially quadrilateral lamination layers.

,Fig. 3 is a face view of a half coil formed as by cutting through both of the sides of a coil like that of Fig. l

ing the assembly of a rectangular stack of nested laminations.

Fig. 5 is an exploded perspective view of part of the lamination layers as from the U-shaped bundle of Fig. 3.

Fig. 6 is a perspective view of the preferred embodiment of three-phase core for transformers in accordance with the present invention, with phase windings being indicated in dotted lines.

Fig. 7 is a fragmentary sectional view on an enlarged scale taken as on the line VII-VII of Fig. 6.

Fig. 8 is a face view of a coil similar to the coil of Fig.

1, but including a lesser number of turns.

Fig. 9 is a face view of the coil of Fig. 8 with the short sides thereof parted along a line parallel to, but offset from the longitudinal center line of the coil to provide two substantially U-shaped bundles of lamination layers.

Fig. 10 is a face view of a modified U-shaped bundle of lamination layers formed by alternately stacking the lamination layers of the bundles of Fig. 9.

Fig. 11 is a perspective view of a three-phase core for transformers embodying the modified third leg of Fig. 10; and

Fig. 12 is a fragmentary sectional view on an enlarged scale taken along a plane longitudinally bisecting the third leg of the core of Fig. 11, and'bisecting the yoke joints.

Referring now to the drawings in which the various parts are indicated by numerals, it will be seen, particularly from Figs. 6 and 11, that the present invention relates to a three-phase T-core structure. In each of the alternative forms illustrated in the drawings a substan tially rectangular stack 11 of nested rectangular and independent lamination layers 12 is employed, providing parallel winding leg portions 13, 15, and yoke portions In the form ofthe structure illustrated in Fig. 6 a substantially U-shaped bundle 19 of independent lamination layers 20 is associated with stack 11, and when so associated provides a third or middle winding leg portion 21, and connecting yoke portions 23, 24.

Preferably and in order to facilitate the preparation of lamination layers 12, suitable magnetic strip material is withdrawn from a source of supply (not shown) and engaged as upon a mandrel 25, the mandrel 25 being rotated and forming of the strip material a continuou coil C of generally rectangular shape. For convenience it is preferred that the mandrel be rotatably supported as upon a suitable shaft 26. During the rotation of the mandrel in the formation of coil C suitable spacers 27 are interposed between the short sides of the successive layers of the strip material so as to provide, upon completion of the coil, spacings between the respective adjacent layers at the short sides of the coil. After a suitable length of the/magnetic material has been wound into the coil, the coil may be subjected to strain relieving annealing.

A coil C is cut through a common short side of each ofits turns as shown in Fig. 2 substantially at the center of the severed short sides. Such parting of the turns of coil C creates a nest 'of substantially rectangular independent lamination layers 12, each having opposite elongated leg portions 28, an uninterrupted short side 29, and ,a severed short side 30, having a gap 31.

The rectangular layers 12 are preferably unnested from the arrangement shown in Fig. 2 and are successively short sides 30 'are inserted through the windows of the phase windings, and upon competion of such insertion are moved into butt jointed relationship closing the gap '31 of the next adjacent layer 12 is positioned in the opposite yoke portion of stack 11. Such alternate positioning of rectangular layers 12 is illustrated in Fig. 4 typifying the assembly relationship of the rectangular layers prior to introduction to the phase windings. A similar coil C is severed through both of the opposite short sides substantially along the center line of the short sides to produce a bundle 19 of substantially. U-shaped lamination layers 20. The lamination layers 20 of bundle 19 are successively threaded through the window of a third phase winding 35 to position winding leg 21 in relationship to the phase winding 35, with yoke portions 23, 24 projecting substantially at right angles thereto and being of substantially uniform length. The third leg yoke portions 23, 24 are respectively interleaved between adjacent lamination layers of yoke portions 17, 18 of stack 11, and the third leg yoke portions are of a length to extend the entire Width of the strip material of the respective rectangular layers 12. The spaces created by spacers 27 as described hereinabove efficiently provide for the reception of such interleaving with the rectangular lamination layers without disrupting the jointing in such rectangular layers.

It thus will be seen that in the completed core, as illustrated in Fig. 6, half of the lamination layers in yoke portion 17 are uninterrupted portions 29, and the remaining half of the lamination layers in yoke portion 17 are severed portions 30, each provided with a butt jointclosing its gap 31. In each instance the butt jointed portions of the lamination layer sides 30 are lapped adjacent the butt joint and on their opposite faces by the interleaved yoke portions 23 of lamination layers 20.

It will further be observed that a similar condition obtains in yoke portion 18 in which each of the lamination layers 12 which is butt jointed in yoke portion 17 is continuous through yoke portion 18, and the remaining lamination layers 12, continuous through yoke portion 17, are respectively butt jointed in yoke portion 18 and butt joints lapped by third leg yoke portions 24.

In the modified form illustrated in Fig. 11, as stated, a stack 11 of substantially rectangular lamination layers 12 is likewise employed, the principal modification lying in the formation of the U-shaped bundle from which the third leg of the core is formed. In this modification a separate coil C is formed as by winding a suitable length of the magnetic strip material upon a mandrel 25, the winding being continued to produce a coil preferably having half the number of turns formed in coil C. During the winding, as in the winding of coil C, suitable spacers 27 are succesively inserted between the adjacent short sides of the layers of coil C.

The opposite short sides of coil C are severed as at 41, 42, the respective cuts being formed along a line offset from and parallel to the longitudinal center line of coil C. This severing of coil C produces a U-shaped bundle of major lamination layers 120, and a second bundle of lesser lamination layers 220. Each of the lamination layers 120, 220 includes an elongated leg portion and yoke portions bent substantially at right angles to the leg portions, the yoke portions of laminations being of a length exceeding the length of the yoke portions of laminations 220 by an amount substantially equal to the width of the strip material from which the lamination layers are formed.

U-shaped layers 120, 220 are unstacked from the respective bundles formed by the severing of coil C and are reassembled into a substantially U-shaped bundle 119 in which the respective lamination layers 120, 220 are alternated, as best shown in Fig. 10. The bundle 119 includes a winding leg portion 121 formed of the layers 120, 220, and yoke portions 123, 124 formed of the yoke portions of the respective layers 120, 220, each of the yoke portions 123, .124 including alternate short and long layer portions.

The respective layers of bundle 119 are threaded through the window of a phase winding 35, and are then associated with the lamination layers of a stack 11. The elongated yoke portions of layers 120 are interleaved between adjacent lamination layers 12 of stack 11, and the square ends of the shorter yoke portions of laminations 220 are each abutted against an edge of a lapped lamination layer '12. It thus will be seen that the bulk or thickness of the joint formed in the T-shaped yoke portion of this alternative embodiment of the core is reduced, enabling a space saving, while preserving through the present arrangement a highly satisfactory jointing between the respective parallel paths for flux flow.

It will be understood that while rectangular lamination layers 12 are preferably and most conveniently formed in the manner described by severing a continuous coil of magnetic strip material, they may be formed otherwise, a for example by successively bending individual lengths of strip material into substantially rectangular form having opposite leg portions, a continuous short side, and an opposite short side including a gap.

When the core is associated with the phase windings, the completed assembly may be mounted in a suitable tank-like container, not shown.

The term lamination layer has been used since one, or more than one, turn or lamination of strip material may be included therein.

I claim:

1. A method of forming three-phase cores for transformers, which comprises the steps of forming a substantially rectangular coil of a plurality of turns of magnetic strip material, inserting spacers during such forming between short sides of adjacent said turns to establish spaces between said adjacent turn short sides, severing said coil along one short side thereof to produce a nested series of a plurality of independent progressively enlarging substantially rectangular lamination layers, each having a severed short side, reversing end for end the nested position of alternate said layers to form a substantially rectangular nested stack of lamination layers having opposite substantially coplanar winding legs and connecting yoke portions with alternate said layers in each said yoke portion being severed and the remaining said layers in each said yoke portion being uninterrupted and adjacent said layer yoke portions having spaces therebetween, respectively abutting the free ends of the severed said layers to form butt joints therebetween in said yoke portions, producing a substantially U-shaped bundle of a like plurality of lamination layers, and interleaving the ends of said bundle layers in the spaces in said stack yoke portions in substantially perpendicular relation, positioning said bundle layers during interleaving with one of the interleaved ends of each bundle layer in lapping relation with the butt joints in said rectangular layers, whereby to form a three-phase T-core for transformers.

2. A method of forming three-phase cores for transformers, which comprises the steps of forming a substantially rectangular coil of a plurality of turns of magnetic strip material, inserting spacers during such forming between short sides of adjacent said turns to establish spaces between said adjacent turn short sides, severing said coil along one short side thereof to produce a nested series of a plurality of progressively enlarging substantially rectangular lamination layers, each having a severed short side, reversing end for end the nested position of alternate said layers to form a substantially rectangular nested stack of lamination layers having opposite substantially coplanar winding legs and connecting yoke portions with alternate said layers in each said yoke portion being severed and the remaining said layers in each said yoke portion being uninterrupted and adjacent said layer yoke portions having spaces therebetween, respectively abutting the free ends of the severed said layers to form butt joints therebetween in said yoke portions, producing a substantially U-shaped bundle of a like plurality of lamination layers, and interleaving the ends of at least part of said bundle layers in the spaces in said stack yoke portions in substantially perpendicular relation, positioning said bundle layers during interleaving with one of the interleaved ends of each bundle layer in said part in lapping relation with the butt joints in said rectangular layers, whereby to form a threeaphase core for transformers.

3. A method of forming three-phase cores for transformers, which comprises the stepsof forming a substantially rectangular coil of a plurality of turns of magnetic strip material, inserting spacers during such forming between short sides of adjacent said turns to establish spaces between said adjacent turn short sides, severing said coil along one short side thereof to produce a nested series of a plurality of progressively enlarging substantially rectangular lamination layers, each having a severed short side, reversing end for end the nested position of alternate said layers to form a substantially rectangular nested stack of lamination layers having opposite substantially coplanar winding legs and connecting yoke portions with alternate said layers in each said yoke portion being severed and the remaining said layers in each said yoke portion being uninterrupted and adjacent said layer yoke portions having spaces therebetween, respectively abutting the free ends of the severed said layers to form butt joints therebetween in said yoke portions, producing a substantially U-shaped bundle of a like plurality of lamination layers in which alternate said U-shaped layers have ends of a uniform length in excess of the ends of the remaining U-shaped layers, interleaving the ends of said alternate bundle layers in the spaces in said stack yoke portions to position said alternate bundle layers during interleaving with one of the interleaved ends of each said .alternate layer in lapping relation to said rectangular layer butt joints and abutting the ends of said remaining bundle layers in butt joints against edge portions of said stack yoke portions to position the remaining said bundle layers during abutting with one of the abutted ends of each said remaining layer butting said rectangular layer butt joints, whereby to form a three-phase T-COre for transformers.

4. A method of forming three-phase cores for transformers, which comprises the steps of winding magnetic strip material to form a substantially rectangular coil of a number of turns of said material having a pair of substantially parallel short sides and a pair of substantially parallel long sides, during said winding inserting spacers between the short sides of adjacent said turns to establish spaces therebetween; severing said coil across one of said short sides only to produce a nest of a like number of individual, quadrilateral, lamination layers, each quadrilateral layer being severed across one short side only, unnesting the layers of said nest, successively associating both the long sides of each quadrilateral layer with phase windings to provide uninterrupted winding legs comprising said long sides connected by yokes comprising said short sides, during associating of said layer long sides with said phase windings alternately positioning said severed short sides in opposite yoke portions and butting the ends of said severed short sides to joint said quadrilateral layers, said yokes consisting of alternate uninterrupted short sides and butt jointed short sides and maintaining the spaces established during winding between said short sides in said yokes; forming a pair of pluralities of substantially U-shaped lamination layers each substantially equal in number to one-half said number of turns and each U-shaped layer having an elongated leg portion and relatively short portions connected to said leg portion,

7 the short portions of one of said pluralities of U-shaped layers being formed of a length to project a distance substantially equal to the width of said strip material beyond the short portions of the other said plurality of U-shaped layers when said pluralities are stacked together, alternately nesting layers from the respective said pluralities of U-shaped layers to provide a substantially U-shaped bundleof layers having alternate longer and f lesser short portions projecting from said leg portions, associating the bundle leg with an additional phase winding, interleaving the short portions of said one plurality of bundle laminations into the spaces in said stack yokes,

abutting the short portions of the other plurality of bundle bundle laminations, during interleaving with one of the interleaved short portions of each bundle lamination of 'laminations against said stack yokes, to position said 8 said one plurality in lapping relation with the respective butt joints in said quadrilateral layers and with one of the abutted short portions of each bundle lamination of References Cited in the file of this patent UNITED STATES PATENTS Acly Nov. 14, 1933 2,489,625 Dornbush Nov. 29, 1949 2,516,164 Vienneau July 25, 1950 2,594,002 Ellis et a1. Q. Apr. 22, 1952 

